The Common carp (Cyprinus carpio) is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia. The wild populations are considered vulnerable to extinction, even the so-called "wild" strain that was brought, already domesticated, to England in the Middle Ages. However, the species has also been domesticated and introduced into environments worldwide, and is often (as in Australia) considered an invasive species and treated as vermin
There are various patterns of scaling,and various patterns of coloration, which are all achieved by selective breeding. For example - the Mirror Carp - which is not a separate species, nor are the "frame" carp , the "linear mirror", nor the various coloured varieties such as "koi" carp and Ghost Carp. They are all the same species, just as Alsatian dogs, Fox Terriers, Greyhounds and Cocker Spaniels are all the same species.
Numerous domesticated strains include the Aischgrund, the Galician, the Koi, the Italian and many others.
Common carp can grow to a maximum length of 120 cm, a maximum weight of over 40 kg, and an oldest recorded age of at least 65 years. The largest recorded carp, caught by an angler in January 2010 at Lac de curtons (Rainbow Lake) near Bordeaux, France, weighed 42.6 kg. The wild, non-domesticated forms tend to be much less stocky at around 20% - 33% the maximum size.
Although they are very tolerant of most conditions, common carp prefer large bodies of slow or standing water and soft, vegetative sediments. A schooling fish, they prefer to be in groups of 5 or more. They naturally live in a temperate climate in fresh or slightly brackish water with a pH of 6.5 - 9.0 and salinity up to about 5‰, and temperatures of 3 to 35 °C. The ideal temperature is 23 to 30 °C, with spawning beginning at 17-18 °C; they will readily survive winter in a frozen over pond, as long as some free water remains below the ice. Carp are able to tolerate water with very low oxygen levels, by gulping air at the surface.
Common carp are omnivorous. They can eat a vegetarian diet of water plants, but prefers to scavenge the bottom for insects, crustaceans (including zooplankton), and benthic worms.
An egg-layer, a typical adult fish can lay 300,000 eggs in a single spawning. Although carp typically spawn in the spring, in response to rising water temperatures and rain fall, carp can spawn multiple times in a season. In commercial operations spawning is often stimulated by injection.
A single carp can lay over a million eggs in a year, yet their population remains the same, so the eggs and young perish in similar vast numbers. Eggs and fry often fall victim to bacteria, fungi, and the vast array of tiny predators in the pond environment. Carp which survive to juvenile are preyed upon by other fish such as the northern pike and largemouth bass, and a number of birds (including cormorants, herons, goosander, and osprey) and mammals (including otter and mink).
Common carp are extremely popular with anglers in many parts of Europe, and their popularity as quarry is slowly increasing among anglers in the United States (though destroyed as pests in many areas), and southern Canada. Carp are also popular with spear, bow, and fly fishermen.